Sunday, October 9, 2011

Elephant birds were among the heaviest birds that have ever existed. Following the extinction of the last dinosaurs 65 million years ago, the mighty reptiles that had dominated the earth for more than 160 million years, the long overshadowed birds and mammals evolved into a great variety of new species, some of which gave rise to giants like the elephant bird.

In their general appearance, elephant birds were similar to the fiightless birds called “ratites” with which we are familiar today, such as the emu ( Dromaius novaehollandiae ), ostrich ( Struthio camelus ), rhea ( Rhea sp.), cassowary ( Casuarius sp.), and kiwi ( Apteryx sp.); however, the biggest elephant bird, Aepyornis maxiumus, was enormous. It was about 3 m tall and probably weighed about 450 kg (the giant moa of New Zealand was actually taller but was way behind the elephant bird in terms of bulkmoa are discussed later in this chapter). On the island of Madagascar, there were few large predators, and the ancestors of the elephant birds had no need to fiy; therefore this ability was gradually lost. Grounded, these birds went on to become animals that were bound to the land. Their skeletons show that they had very powerful legs and that they plodded around Madagascar on their big feet. The wings were reduced to tiny structures and were probably not visible beneath the bird’s plumage. These birds had become so well adapted to a life without fiight that the large and specially modified chest bone (keellike sternum) found in most birds, which serves as an attachment for the wing muscles, had all but disappeared.

We don’t know exactly what the elephant birds ate, but we can assume from the shape of their bill that they were not carnivorous. Some people have suggested that certain Madagascan plants that are very rare today depended on the elephant birds for the dispersal of their seeds. The digestive system of these large birds was ideally suited to breaking down the tough outer skins of these seeds. Some were digested, but others passed through the bird intact and in a state of readiness for germination.

The remains of the elephant bird that have been found to date allow us to build up a picture of how this extinct animal lived. The most intriguing remains are the bird’s eggs. Some have been found intact, and they are gigantic—the largest single cells that have ever existed. They are about three times bigger than the largest dinosaur eggs, with a circumference of about 1 m and a length of more than 30 cm. One of these eggs contained about the same amount of yolk and white as 200 chicken’s eggs. These huge shelled reminders of the elephant bird are occasionally unearthed in the fields of Madagascan farmers, and one is even known to contain a fossilized embryo.

The number of elephant bird species that once inhabited Madagascar is a bone of contention among experts, but it is possible that Madagascar supported several species of these large birds. On their island, surrounded by abundant food and few animals to fear, especially when fully grown, the elephant birds were a successful group of animals. Then, around 2000 years ago, their easy existence was overturned as humans from Africa, Indonesia, and the islands around Australia reached this isolated land of unique natural treasures. Humans by themselves are one thing, but thousands of years ago, humans did not travel alone—they took their domestic animals with them. The elephant birds, in their 60 million years of evolution, never saw a human, and they wouldn’t have recognized them as dangerous. The humans, on the other hand, saw the elephant birds as a bounteous supply of food. Hunting had a disastrous eff ect on the populations of these giant birds. They had evolved in the absence of predation and, as a result, probably reproduced very slowly. To add insult to injury, the animals the humans brought with them—pigs, dogs, rats, and so on—made short work of the elephant bird’s eggs. Other introduced animals, such as chickens, may have harbored diseases to which these giant birds had never been exposed. With no natural immunity to these pathogens, epidemics may have ravaged the populations of elephant birds, which were already under pressure from hunting and egg predation. Changes in climate may have led to the drying out of Madagascar, and this, too, could have aff ected the populations of these impressive birds. The actual extinction timeline for the elephant birds is sketchy, but many experts suppose that the last of these great birds died out before 1600. The means at our disposal for the aging of ancient material are constantly improving, and some recent estimates move the disappearance of these birds into the nineteenth century. It is possible that some stragglers managed to survive until recent times, but we can be certain that no elephant birds survive today.

Remote and treeless, the Falkland Islands is a small archipelago in the South Atlantic Ocean. Ravaged by incessant winds and terrible winter storms, these islands are a very harsh environment. Although the Falklands are a welcome refuge for marine animals such as penguins, seals, and sea lions, very few land animals have managed to make a living on this stark, oceanic outpost. The only mammals known from the Falkland Islands are a small species of mouse and a mysterious dog, the warrah, which also goes by the names of “Falkland Island fox” and “Antarctic wolf. ”

Whether the animal was a fox or a wolf is a bone of contention among mammal experts. Contemporary accounts of the living animal as well as stuff ed skins show that this carnivore had both wolf and fox characteristics. An adult warrah was about twice as big as a red fox (1.6 m long), with a large, wolfish head, but because of its short legs, it was only about 60 cm tall at the shoulder. Its tail, unlike that of a wolf, was thickly furred, and like a fox, it excavated dens in the sandy soil of the coastal dunes. Apart from mice, the land of the Falkland Islands supports precious little prey that sustained the warrah, but it is possible that insect larvae and pupae featured prominently in its diet. Although the interior of the Falkland Islands is rather impoverished when it comes to carnivore food, the coast is a bounteous source of nourishment at certain times of the year. The islands are used by numerous marine animals, including seals, sea lions, penguins, and a variety of fl ying seabirds. When these animals were raising their young, times must have been good for the warrah, and it probably made off with eggs, nestlings, adult birds, and even young pinnipeds. To reach these good supplies of food, the warrah traveled along well-worn paths that must have been made by generations of the animals accessing their feeding grounds via the shortest possible route. Although the southern spring and summer was a time of abundance for the warrah, the autumn and winter were probably very tough, and some accounts from the eighteenth and nineteenth centuries report that the living animals looked starved and very thin.

Regardless of its wintertime depravations, the warrah, in the absence of competition, appears to have been a successful species that was quite numerous on the two main islands of the Falklands group. This monopoly came to an end with the arrival of humans. Initially, visitors to the Falkland Islands were afraid of the warrah as it would wade into the water to meet an approaching boat. This was not an act of aggression, but an act of curiosity. The warrah had probably never seen humans and had therefore never learned to be afraid of them, an unfortunate fact that contributed to the extinction of this interesting dog.

Although the Falkland Islands are a harsh place, certain breeds of hardy sheep were well suited to the conditions, and they were introduced to the islands as a way of laying the foundations for the first human colonies on the islands. The sheep thrived on the islands, and as humanity tightened its grip on the Falklands, the warrah was seen as a menace that had to be exterminated. Like all dogs, the warrah was an opportunistic feeder, and it undoubtedly fed on the introduced sheep and lambs that nibbled the Falkland Island grass, but islanders, in their ignorance, believed the warrah was a vampire that killed sheep and lambs to suck their blood, only resorting to meat eating in times of desperation. Horrific myths can be very compelling, especially on a group of small islands where news travels fast and where livelihoods are at stake. In an attempt to quell the populace, the colonial government of the Falkland Islands ordered a bounty on the warrah, and fur hunters soon moved in to collect handsome rewards for delivering the pelts of dead animals.

The Falkland Islands, with a land area roughly the size of Connecticut, could never have supported huge numbers of warrah. Even before the human invasion, the warrah population was probably no more than a few thousand individuals, and it is therefore no surprise to learn that hunting quickly led to the extermination of this animal. Because the warrah was so very tame, hunting was a breeze, and all the hunter needed was a piece of meat and a knife. He held out the piece of meat to tempt the animal and stabbed it with the knife when it came within range. Other hunters used rifl es or poison, but regardless of which particular method was used to kill the warrah, it was exceedingly rare by the 1860s.

Amazingly, a live warrah found itself in London Zoo in 1868 after being transported on a ship with a menagerie of other exotic animals, most of which perished during the journey. This warrah, far from home, survived for several years in the zoo, but it was one of the last of its species. Back in the South Atlantic, the onslaught of the sheep farmers and the hunters was too much for the poor warrah, and in 1876, the last known animal was killed at Shallow Bay in the Hill Cove Canyon.